Adam Clarke on Exodus 30:7

When he dresseth the lamps - Prepares the wicks, and puts in fresh oil for the evening.

Shall burn incense upon it - Where so many sacrifices were offered it was essentially necessary to have some pleasing perfume to counteract the disagreeable smells that must have arisen from the slaughter of so many animals, the sprinkling of so much blood, and the burning of so much flesh, etc. The perfume that was to be burnt on this altar is described Exo 30:34. No blood was ever sprinkled on this altar, except on the day of general expiation, which happened only once in the year, Exo 30:10. But the perfume was necessary in every part of the tabernacle and its environs.